1. Field of the Invention
This invention relates to a liquid crystal display apparatus and, more particularly, to a TFT liquid crystal display apparatus which prevents display non-uniformity caused by a non-uniform distribution of static electricity on the surface of the liquid crystal display apparatus.
2. Description of the Prior Art
FIG. 1 shows the section of a usual, conventional liquid crystal display apparatus. As shown in FIG. 1, a liquid crystal display apparatus 20 is constituted by a TFT substrate 22a which is made of, e.g., a transparent glass having an electrode on its inner surface, an opposite substrate 22b which is also made of, e.g., a transparent glass having an electrode on its inner surface and arranged in parallel to the TFT substrate 22a via a spacer/sealing member 24, a liquid crystal 26 liquid-tightly sealed among the pair of substrates 22a, 22b and the spacer/sealing member 24, a color filter 27 adhered to the inner surface of the opposite substrate 22b, a pair of polarizing plates 28 and 29 respectively adhered to the outer surfaces of the TFT substrate 22a and the opposite substrate 22b, and protective films 23 and 25 respectively adhered to the outer surfaces of the polarizing plates 28 and 29. The polarizing plates 28 and 29 are readily chargeable, and therefore when the protective films 23 and 25 respectively adhered to the outer surfaces of the pair of polarizing plates 28, 29 are peeled off during manufacturing processes of the liquid crystal display apparatus or just before use after the liquid crystal display apparatus has been forwarded to the user, static electricity is generated on the outer surfaces of the polarizing plates 28 and 29.
Since the polarizing plate 28 is formed of an insulating film, static electricity generated by peeling of the protective film 23 is locally electrified at a part of the outer surface of the polarizing plate 28, and this nonuniform static electricity causes display non-uniformity. An IPS (In-Plane Switching) liquid crystal panel uses the same polarizing plate as a TN (Twisted Nematic) liquid crystal panel. In the conventional panel, when the protective films 23 and 25 are peeled off, the removal of electrification of the static electricity is done for a long time to suppress display non-uniformity.
FIG. 2 is a plan view showing a conventional polarizing plate 40 when the surface is not coated with any high-resistance conductive agent, and the protective film is peeled off. When the protective film is peeled off, static electricity is generated on the surface of the polarizing plate 40. At this time, since the conventional polarizing plate 40 has a high surface resistance (1xc3x971016 ohm or more), the generated static electricity is not uniformly distributed, and the potential locally increases, as shown in FIG. 2. These high-potential portions result in display non-uniformity, which requires the removal of electrification of the static electricity for a long time (about 1 min).
However, the long-time removal of electrification of the static electricity for suppressing display non-uniformity of the display apparatus decreases productivity, so the removal time of the electrification must be shortened. In the IPS panel, even if display non-uniformity is suppressed by the long-time removal of the electrification, static electricity may still be generated on the outer surface of the polarizing plate when the polarizing plate rubs against the backlight.
That is, if the polarizing plate contacts the diffusion sheet of the backlight due to vibration, shock, or the like after assembling the backlight, static electricity is generated on the outer surface of the polarizing plate. For the same reason as described above, the potential locally increases to generate electrified portions, resulting in display non-uniformity.
Another conventional liquid crystal display apparatus in which, in order to prevent the surface of the polarizing plate from generating a locally electrified portion due to the static electricity, an organic conductive film is formed on a polarizing plate is disclosed in Japanese Unexamined Patent Publication No. 10-96953. The organic conductive film used in this conventional liquid crystal display unit has a surface resistance of 1xc3x97105 ohm. However, in order to secure such a low surface resistance, the organic conductive film must be so formed as to have a remarkably high thickness even if the most suitable material for the organic conductive film, which is available at present, is used. As a result, it causes the organic conductive film to decrease its transparency, resulting in having a bad effect upon the liquid crystal display apparatus.
The present invention has been made in consideration of the conventional situation, and has as its object to provide a liquid crystal display apparatus in which static electricity is uniformly distributed on the surface of an IPS panel so as to prevent any display non-uniformity even when a protective film is peeled off.
In order to achieve the above object, according to the first aspect of the present invention, there is provided a liquid crystal display apparatus in which a backlight unit is mounted on one surface side thereof, and in which a liquid crystal is sealed between a pair of transparent substrates, comprising a conductive film made of a high-resistance conductive agent and formed on an outer surface of a polarizing plate adhered to an outer surface of one transparent substrate mounted on the side of said backlight unit so as to secure a surface resistance of from 1xc3x97109 ohm to 1xc3x971012 ohm for the polarizing plate.
According to the second aspect of the present invention, there is provided a liquid crystal display apparatus in which a backlight unit is mounted on one surface side thereof, in which a liquid crystal is sealed between a pair of transparent substrates, in which a color filter is adhered to an inner surface of one of said pair of transparent substrates, which is mounted on the side opposite to the side of said backlight unit, and in which polarizing plates are respectively adhered to outer surfaces of said pair of transparent substrates, comprising a conductive film made of a high-resistance conductive agent and formed on an outer surface of the polarizing plate adhered to an outer surface of one of said pair of transparent substrate mounted on the side of said backlight unit so as to secure a surface resistance of from 1xc3x97109 ohm to 1xc3x971012 ohm for the polarizing plate.
The high-resistance conductive agent in the first and second aspects has a composition of not more than 1% of a trialkyl-(2-hydroxyethyl) ammonium salt, not more than 10% of pentaerythritol, and not less than 90% of ethanol, or a composition of 5% of tin oxide, 2 to 5% of tetraethoxysilane, 1 to 2% of a polyester resin, and 87 to 90% of water.
The liquid crystal display apparatus in the first and second aspects may be an IPS panel.
According to the present invention having these aspects, the high-resistance conductive film is formed on the surface of the polarizing plate. Even if the protective film is peeled off from the polarizing plate, static electricity is not locally electrified on the polarizing plate, but is uniformly distributed, and no working time for removing static electricity is required.
Even if static electricity is generated between the liquid crystal display apparatus and backlight upon assembling the backlight, no display non-uniformity by the generated static electricity occurs.
The above and many other objects, features and advantages of the present invention will become manifest to those skilled in the art upon making reference to the following detailed description and accompanying drawings in which preferred embodiments incorporating the principle of the present invention are shown by way of illustrative examples.